bd509ececdf0

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/2021/02.txt	Thu Dec 02 00:28:53 2021 -0500
@@ -0,0 +1,1000 @@
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--- a/src/2020/days/day-11.lisp	Wed Dec 01 21:48:27 2021 -0500
+++ b/src/2020/days/day-11.lisp	Thu Dec 02 00:28:53 2021 -0500
@@ -5,13 +5,9 @@
   (when (array-in-bounds-p seats row col)
     (aref seats row col)))
 
-(defun count-neighbors (seats row col &aux (result 0))
-  (do-irange ((dr -1 1)
-              (dc -1 1))
-    (unless (= 0 dr dc)
-      (when (eql #\# (sref seats (+ row dr) (+ col dc)))
-        (incf result))))
-  result)
+(defun count-neighbors (seats row col)
+  (iterate (for (r c) :within-radius 1 :origin (row col) :skip-origin t)
+           (counting (eql #\# (sref seats r c)))))
 
 (defun count-visible (seats row col &aux (result 0))
   (do-irange ((dr -1 1)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/2021/days/day-02.lisp	Thu Dec 02 00:28:53 2021 -0500
@@ -0,0 +1,37 @@
+(advent:defpackage* :advent/2021/02)
+(in-package :advent/2021/02)
+
+(defun parse (stream)
+  (iterate (for line :in-stream stream :using #'read-line)
+           (ppcre:register-groups-bind ((#'ensure-keyword command) (#'parse-integer n))
+               ("(\\w+) (\\d+)" line)
+             (collect (cons command n)))))
+
+(defun horiz (pos) (realpart pos))
+(defun depth (pos) (imagpart pos))
+
+(defun part1 (course)
+  (iterate (for (cmd . n) :in course)
+           (summing (ecase cmd
+                      (:forward (complex n 0))
+                      (:down    (complex 0 n))
+                      (:up      (complex 0 (- n)))))))
+
+(defun part2 (course)
+  (iterate (with pos = 0)
+           (with aim = 0)
+           (for (cmd . n) :in course)
+           (ecase cmd
+             (:forward (incf pos (complex n (* n aim))))
+             (:down    (incf aim n))
+             (:up      (decf aim n)))
+           (returning pos)))
+
+(define-problem (2021 2) (data) (1660158 1604592846)
+  (let* ((course (parse data))
+         (p1 (part1 course))
+         (p2 (part2 course)))
+    (values (* (horiz p1) (depth p1))
+            (* (horiz p2) (depth p2)))))
+
+#; Scratch --------------------------------------------------------------------